1. Field of the invention:
The present invention relates to an enclosing type electric compressor.
2. Description of the prior art:
It is well known that in a scroll compressor having low vibration and low noise characteristics a suction chamber is provided at the outer periphery thereof, a discharge port is installed at the center of an eddy thereof, the compressed fluid may flow only in one way, and this scroll compressor does not need a discharge valve to compress fluid as provided in a reciprocation type or a rotary type compressor and does not require any large space for discharge since the compression load fluctuation and discharge pulsation of the scroll compressor are comparatively small.
Such a structure of this kind as shown in FIG. 4 is well known as a compressor with a high pressure gas-enclosed vessel. This conventional structure is so composed that a drive spindle 207 is supposed on the internal wall of a cylindrical portion of an enclosed casing 226 as fixing means of a compression portion and an electric motor and as supporting means of the drive spindle 207 onto a thin steel-made enclosing casing 226 having good extensibility, which has been produced for lightening the weight of components and lowering the production costs, the extreme outer peripheral portion of steel-made frame 203 having good rigidity, by which stationary scroll 202 is fixed, is pressed and fixed therein, a stator 216 of the electric motor is fixed with bolts (not shown) at the lower part of the frame 203, and the drive spindle 207 is supported by means of bearings 218 and 214 of the projection 299 toward the side of the electric motor. (Japanese Laid-Open Pat. Publication No. 59-110884).
Also, as shown in FIG. 5, in another structure that a stator of the electric motor 303 is pressed and fixed on the internal wall of the enclosing casing 301, the outer peripheral portion of the frame 306 of the compression portion by which the drive spindle 307 is supported is pressed and fixed at the lower internal wall of the enclosing casing 301, and the drive spindle 307 is supported by the projection 399 at the electric motor side of the frame 306 is known, too. (Japanese Laid-Open Pat. Publication No. 57-8386).
However, in such a construction a stator 216 whose weight is comparatively heavy, is fixed only at the end of the frame 203 as shown in FIG. 4, the clearance between the outer periphery of a rotor 215 of the electric motor and the inner periphery of the stator 216 is imbalanced, and fluctuation may be generated in force by which the rotor 215 is electrically attracted to the stator 216 when the drive spindle 207 supported by the bearings 218 and 214 rotates, thereby causing the drive spindle to be bent. Furthermore, load operating on the bearings 218 and 214 and an electromagnetic reaction force operating on the fixing end portion of electric motor of the frame 203 fluctuate and become excessive by overlapping the centrifugal force of the rotor 215 thereon. For this reason, the frame 203 and the enclosing case 226 vibrate and cause noises. In addition, as the bearing of the drive spindle 207 is supported only by the frame 203, the distance between the bearings 218 and 214 cannot be sufficiently long and the angles of inclination of the drive spindle, which may be generated within the range of the clearance of the bearings, become large. For this reason, biased contact may occur on the sliding surface of the bearings 218 and 214, thereby causing the bearings to be exposed to abnormal wearing and seizure.
In such a construction that the stator of the electric motor 303 and the frame 306 of the compression portion are separately pressed and fixed on the inner wall of the cylindrical portion of the enclosing casing 301 and the drive spindle 307 is supported only by the frame 306 as shown in FIG. 5, there is a problem that electromagnetic vibrations of the electric motor 303 and vibrations of the frame 306, resulting from scattering of the clearance between the stator and the rotor of the electric motor 303 as well as in the above case, may spoil various characteristics of a scroll compressor such as low vibration, low noise, high efficiency and high reliability.
As a method to remove the above-mentioned problems, USP 4,160,629 discloses a scroll compressor with a construction that the drive spindle is supported at both the ends of an electric motor. In this case, the enclosing case, the electric motor and bearings at two points are separately composed, and it is very difficult to attain completed axial alignment among these components, resulting in such various problems as biased contact of the bearings, an increase in input and a lowering of durability. Thus, it has been highly expected that an enclosed type electric compressor having high compression efficiency, high durability, low vibration, and little noise will be developed.